garyweb3 Posted July 18, 2023 Share Posted July 18, 2023 I have a 2.5L engine in my 1987 Comanche. I am trying to adjust the TPS to factory specs according to the TSM. It says that the voltage reading between terminals B and C should be 5v at WOT. That's what I get but it also reads 5v with the throttle closed. It doesn't vary from closed to open. The TSM doesn't give a voltage spec at closed. Does this seem right? When I check between terminals A and B it changes from less than 1v to 4.7v which looks to be correct according to the manual. Link to comment Share on other sites More sharing options...
eaglescout526 Posted July 18, 2023 Share Posted July 18, 2023 Have we verified we’re probing the right terminals? Silly I know but let’s start there. Link to comment Share on other sites More sharing options...
garyweb3 Posted July 18, 2023 Author Share Posted July 18, 2023 According to the picture in the TSM I used the correct ones. Link to comment Share on other sites More sharing options...
eaglescout526 Posted July 18, 2023 Share Posted July 18, 2023 I’ll have to help when I get home. I wish I had the TBI book on my phone. Link to comment Share on other sites More sharing options...
zomeizter Posted July 18, 2023 Share Posted July 18, 2023 The check is done on the signal wire and the sensor ground wire (or chassis ground alternatively), do not probe the 5v supply wire. Ensure the connector is solid on the sensor and that the actuator lever from the throttle is engaging the sensor. If no change in voltage occurs when you rotate the throttle plate, you have a defective TPS. I went through this exact sensor failure on my XJ just yesterday. Link to comment Share on other sites More sharing options...
Ωhm Posted July 18, 2023 Share Posted July 18, 2023 3 hours ago, garyweb3 said: It says that the voltage reading between terminals B and C should be 5v at WOT. B and C should read 5vdc. It's the MAP sensor supply voltage. I don't know why they say a WOT. Link to comment Share on other sites More sharing options...
garyweb3 Posted July 19, 2023 Author Share Posted July 19, 2023 WOT stands for Wide Open Throttle. Link to comment Share on other sites More sharing options...
garyweb3 Posted July 19, 2023 Author Share Posted July 19, 2023 23 hours ago, zomeizter said: The check is done on the signal wire and the sensor ground wire (or chassis ground alternatively), do not probe the 5v supply wire. Ensure the connector is solid on the sensor and that the actuator lever from the throttle is engaging the sensor. If no change in voltage occurs when you rotate the throttle plate, you have a defective TPS. I went through this exact sensor failure on my XJ just yesterday. I'm going by the directions in the TSM. Link to comment Share on other sites More sharing options...
garyweb3 Posted July 22, 2023 Author Share Posted July 22, 2023 On 7/18/2023 at 5:08 PM, zomeizter said: The check is done on the signal wire and the sensor ground wire (or chassis ground alternatively), do not probe the 5v supply wire. Ensure the connector is solid on the sensor and that the actuator lever from the throttle is engaging the sensor. If no change in voltage occurs when you rotate the throttle plate, you have a defective TPS. I went through this exact sensor failure on my XJ just yesterday. What were the symptoms that caused you to suspect the TSP was bad? Link to comment Share on other sites More sharing options...
cruiser54 Posted July 22, 2023 Share Posted July 22, 2023 The letters are generally embossed on the connectors. Link to comment Share on other sites More sharing options...
garyweb3 Posted July 23, 2023 Author Share Posted July 23, 2023 So if I don't get any variation in voltage between points B and C that means the sensor is bad? Link to comment Share on other sites More sharing options...
zomeizter Posted July 23, 2023 Share Posted July 23, 2023 12 minutes ago, garyweb3 said: So if I don't get any variation in voltage between points B and C that means the sensor is bad? Correct, but make sure both circuits are good first, 5v supply and solid ground. Link to comment Share on other sites More sharing options...
zomeizter Posted July 23, 2023 Share Posted July 23, 2023 On 7/21/2023 at 6:45 PM, garyweb3 said: What were the symptoms that caused you to suspect the TSP was bad? One of the symptoms was that the transmission shifts were super late and overdrive would never engage. Cruise control was inoperative. Once I hooked up my OBDII code reader, there was a TPS voltage high fault so I proceeded to check it out with a meter since my reader is unable to show me live data off the PCM. Link to comment Share on other sites More sharing options...
garyweb3 Posted July 23, 2023 Author Share Posted July 23, 2023 I wish I could use an OBDII reader on my truck. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 23, 2023 Share Posted July 23, 2023 do it the old fashioned way. On Renix, the TPS is 2 parts. One side for engine management and one for auto trans. They work opposite and independent of each other. Link to comment Share on other sites More sharing options...
garyweb3 Posted July 24, 2023 Author Share Posted July 24, 2023 10 hours ago, cruiser54 said: do it the old fashioned way. On Renix, the TPS is 2 parts. One side for engine management and one for auto trans. They work opposite and independent of each other. I have a standard transmission. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 24, 2023 Share Posted July 24, 2023 Okay. Then you only have the flat 3-wire connector in use? It's okay if you have a TPS from an auto trans vehicle. You just don't use the square 4-wire pigtail. But, you must take your readings from the flat 3-wire connector. Link to comment Share on other sites More sharing options...
garyweb3 Posted July 24, 2023 Author Share Posted July 24, 2023 Yes that's what I did. I tested according to the steps in the TSM. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 24, 2023 Share Posted July 24, 2023 Have you visited my website? Link to comment Share on other sites More sharing options...
garyweb3 Posted July 24, 2023 Author Share Posted July 24, 2023 I have. Is there something I should be aware of? Link to comment Share on other sites More sharing options...
cruiser54 Posted July 25, 2023 Share Posted July 25, 2023 Have you completed tips 1 thru 5? Link to comment Share on other sites More sharing options...
garyweb3 Posted July 25, 2023 Author Share Posted July 25, 2023 I'll have to back and check what they were. Link to comment Share on other sites More sharing options...
garyweb3 Posted July 26, 2023 Author Share Posted July 26, 2023 Looks like I have some work to do. Do all these tips apply to the 2.5 engine? Link to comment Share on other sites More sharing options...
cruiser54 Posted July 26, 2023 Share Posted July 26, 2023 No. But the ground refreshing and connector refreshing need done ASAP Link to comment Share on other sites More sharing options...
garyweb3 Posted July 26, 2023 Author Share Posted July 26, 2023 I may have done the connector on the firewall already but will check. Link to comment Share on other sites More sharing options...
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